MEMS motion measurement system using differential laser Doppler and its key techniques

摘要

Motion analysis of Micro-electro-mechanical system (MEMS) is a powerful diagnostic tool enabling evaluation of the dynamic behaviour and the status of MEMS. A backscattering differential laser Doppler system is presented. The working principle and optical diagram of the system are explained in detail. In accordance with the characteristic of the measurement system, high-performance phase-locked loop is used to delect a weak measurement signal. Then measurement signal is transferred to computer and further analyzed there. Furthermore, a laser focusing method is described to improve the measurement. The focusing system is composed of a spatial filter and an aspheric lens C240TM-A, and focal spot size is less than 50 um. The silicon micromachined resonator is used as an example in experiments, and the resonant frequencies and the mean amplitude of MEMS are determined. Experimental results indicate that dynamic characteristics of MEMS can be measured well.